Preparations containing chlormethiazole, particularly in the form of its acid addition salts, especially, as disclosed in GB 847,520, the acid addition salt with ethanedisulphonic acid, are known to possess valuable therapeutic properties. The general pharmacology and therapeutic applications of chlormethiazole have been extensively reviewed in a recent publication (Acta Psychiatr. Scand., Suppl. 329, 73, 1986). Thus, for example, chlormethiazole possesses sedative and hypnotic properties and is used clinically as a hypnotic in the elderly, particularly in the management of psychogeriatric patients. Chlormethiazole also possesses anticonvulsant properties and is used clinically for the treatment of different types of convulsive states, such as, for example, status epilepticus and pre-eclampsia. Chlormethiazole is also used clinically for the treatment of ethanol (alcohol) withdrawal states including delirium tremens.
The present invention can be distinguished from the above prior art in that it is concerned with a new medical use which is unexpected and which can be clearly distinguished from the applications in the above described disorders. Usefulness in any or all of the above clinical disorders would not suggest or in any way make obvious the use of the compounds which are the subject of the present invention in the prevention and/or treatment of neurodegeneration.
There are a few contradictory reports on the effects of chlormethiazole on cerebral circulation and metabolism. I. Pichlayr and co-workers (Anaesthesist, 1973, 22, 496-500) found that i.v. infusion of chlormethiazole into dogs caused an initial increase in cerebral blood flow, followed by a decrease in both cerebral blood flow and oxygen consumption rate, a finding which they interpreted as indicating that chlormethiazole possibly offers a degree of protection to cerebral functions. Others (J. Pogady, M. Ruscak and J. Orlicky, Activ. Nerv. Sup. (Prague), 1972, 14, 87) have presented results which are interpreted as possibly indicating a deleterious effect of chlormethiazole in situations associated with impaired brain circulation. Significantly, in the most recent study (Acta Anaesth. Scand., 1979, 23, 259-266) Carlsson and Rehncrona were unable to demonstrate either a protective or a detrimental effect of chlormethiazole when it was administered during reversible, incomplete ischaemia in the rat. None of the above studies considered an action of chlormethiazole on neurodegeneration following pathological insult.
The present invention provides a method for the prevention and/or treatment of neurodegeneration in the above mentioned pathological conditions. Thus the new use of chlormethiazole that is the subject of the present invention could not in any way be expected from the above prior art.
Other compounds have been reported to be useful in the prevention and/or treatment of neurodegeneration (see, for example, EP 230 370 and EP 273 309), but there is no drug that is presently accepted as a standard for this use. None of the other compounds thus described would suggest the use of the compound of the present invention for the prevention and/or treatment of neurodegeneration.